Poxvirus proteins which bind to viral DNA and which are present in the virus particle have been solubilized and purified. These proteins will now be characterized in terms of their molecular structure and the mechanisms of interaction with DNA. Particular emphasis will be placed on their ability to alter the structure of DNA. Similar studies will be conducted with proteins that have been isolated from viral DNA factories, which are the sites of viral DNA replication in the cytoplasm of the cell. The protein in the virion of 11,000 molecular weight and the protein in viral DNA factories of 34,000 molecular weight have been identified as basic phosphorylated proteins. The possibility that these proteins interact with DNA in a fashion similar to histones will be investigated. Studies involving nuclear transplantation in cultured cells utilizing cytochalasin enucleation in viral mediated fusion will be continued in order to obtain information regarding cytoplasmic controls of nuclear gene expression. BIBLIOGRAPHIC REFERENCES: Lucas, J.J., G.A. Zorn, A. Brings, E. Szekely and J.R. Kates. 1977. "Recent Developments with Karyoplast Regeneration and Nuclear Transplantation," in Gene Expression and Regulation in Cultured Cells. Third decennial review conference of the Tissue Culture Association. Journal of National Cancer Institute Monographs. Bauer, W.R., E.R. Ressner, J. Kates, and J.V. Patzke. 1977. "A DNA Nicking-closing Enzyme Encapsidated in Vaccinia Virus: Partial Purification and Properties," Proc. Natl. Acad. Sci. U.S.A., May 1977.